It is frequently the case that plural, closely spaced electrical conductors are used to join various elements of a circuit. For example, it is conventional to utilize a bus to connect multiple processing elements of a circuit board or integrated circuit. The bus may include from a few to hundreds of electrical conductors that carry separate signals or voltage references and which need to be isolated from one another. In an integrated circuit, the bus may take the form of parallel channels etched in a dielectric substrate. Such channels may be referred to as “wires” which are “bundled” to form the bus.
One effect that takes place during analog or digital signal transmission is mutual interference amongst the wires of the bus. That is to say, regardless of the fact that a dielectric material separates the channels from one another, the signal in one wire of the bus will influence the signal in each of its nearest neighbour channels. As for the effect on the second-nearest neighbouring channels, this is considerably less significant (since it generally decreases per the cube of the distance), although it may in some cases be noticeable.
As a result of mutual interference, the signal travelling along a given individual wire of the bus will become corrupted. Such an effect may be even more pronounced due to signal degradation resulting from the distance travelled by the signal from its source, in addition to the mutual interference effect. Of course, a signal that arrives in a state where it is either below the noise floor or corrupted under the strong influence of the signal in a neighbouring channel will cause a degradation in the performance of the circuit as a whole.
It would therefore be desirable to reduce the mutual interference amongst the wires of a bus. Accordingly, it is known in the art to “braid” the wires by twisting the entire bundle such that across the length of the braid, each wire takes on a continually changing radial component. For the case of two wires, this results in the formation of a “twisted pair”, which is known to reduce cross-talk. However, although this pattern is simple to achieve in the case of flexible cables by a mere twisting motion, it is extremely prohibitive to attain in the case of printed circuit boards and even more so for an integrated circuit. Specifically, such a design would require individual, isolated, intertwined channels to be defined across the length of a substrate. In fact, it would be impossible to manufacture such a pattern by means of standard lithographic techniques employing layers and vias.
As such, there remains a need in the art to provide a layout which allows a group of electrical conductors to be extended across portions of a circuit board or integrated circuit with reduced mutual interference amongst the conductors.